1. Technical Field
The present invention relates to a grease leakage preventing structure for a gear reducer in a dynamoelectric machine with a gear reducer.
2. Background Art
FIG. 8 illustrates an electric motor with a gear reducer that is one type of dynamoelectric machine with a gear reducer, in which a gear case 104 of a gear reducer 103 is engaged with and integrally assembled with, with bolts, not shown in the drawing, a bracket 102 on a protruding edge thereof, the bracket 102 being press-fitted into an opening end of an electric motor case 101 of an electric motor 100.
In such an electric motor with a gear reducer, in order to smoothly transmit rotation, a structure is employed in which helically cut gear teeth are provided on an output shaft of the electric motor to assemble the shaft with a helical gear of the reducer.
However, a problem may arise in which grease adhered to the helical gear inside the reducer may flow out according to rotation of the gear via the tooth trace of the electric motor output shaft with the helically cut gear teeth and penetrate into the electric motor outside the case.
As a conventional structure for preventing grease leakage in a gear reducer of the electric motor with a gear reducer of this type, a method has been known in which an oil seal is used to prevent the infiltration of grease into the inside of the electric motor.
Referring to FIG. 9, in this method, oil seals 109 are arranged on a base end of a gear tooth portion 106a of an electric motor output shaft 106, which protrudes into an inside of the gear case 104 via an open hole 105a formed on a side panel 105 of the gear reducer 103. The oil seal 109 is arranged on the base end of the gear tooth portion 106a of the electric motor output shaft 106 together with the bearing 107 arranged on the bracket 102 of the electric motor case 101. The helical gear 108 is engaged with the electric motor output shaft 106 in the inside of the gear case 104.
However, in the method using the oil seals 109, because friction load is applied due to the contact between the oil seal and the electric motor output shaft 106, the ratio of loss becomes great in a low-output electric motor. In addition, in providing the oil seals 109, it is necessary to detour around the gear tooth portion 106a of electric motor output shaft 106, and it therefore becomes necessary to design the dimension of the oil seal so that it becomes long enough for detouring around the gear teeth. In particular, in thin-type electric motors, the thickness of the oil seal portion causes a problem.
In this regard, related art is known, as illustrated in FIG. 10, in which a flexible tube 110 is provided so as to cover the gear tooth portion 106a of the electric motor output shaft 106, except for a portion of engagement with the helical gear 108 (see Patent Literature 1).
Furthermore, as illustrated in FIG. 11, related art has been known in which a helical groove 201 is provided, which helically goes around an electric motor output shaft 200 from the side of a bearing of the electric motor toward the side of the gear reducer (see Patent Literature 2).